Police identified the suspect in the shooting that left at least 50 people dead and dozens more injured as 29-year-old Omar Mateen. ABC News reported he was "on the radar" of U.S. officials but was never under specific investigation. An FBI official said Sunday Mateen "may have leanings towards" Islamic extremism.

An aerial view shows the Pulse gay night club after a mass shooting in Orlando, Florida, U.S. June 12, 2016. REUTERS/Carlo Allegri

Friends and family members embrace outside the Orlando Police Headquarters during the investigation of a shooting at the Pulse nightclub, where people were killed by a gunman, in Orlando, Florida, U.S June 12, 2016. REUTERS/Steve Nesius TPX IMAGES OF THE DAY

Friends and family members embrace outside the Orlando Police Headquarters during the investigation of a shooting at the Pulse nightclub, where people were killed by a gunman, in Orlando, Florida, U.S June 12, 2016. REUTERS/Steve Nesius

Friends and family members embrace outside the Orlando Police Headquarters during the investigation of a shooting at the Pulse nightclub, where people were killed by a gunman, in Orlando, Florida, U.S June 12, 2016. REUTERS/Steve Nesius

ORLANDO, FL - JUNE 12: FBI agents investigate near the damaged rear wall of the Pulse Nightclub where Omar Mateen allegedly killed at least 50 people on June 12, 2016 in Orlando, Florida. The mass shooting killed at least 50 people and injuring 53 others in what is the deadliest mass shooting in the country's history. (Photo by Joe Raedle/Getty Images)

ORLANDO, FL - JUNE 12: FBI agents investigate near the damaged rear wall of the Pulse Nightclub where Omar Mateen allegedly killed at least 50 people on June 12, 2016 in Orlando, Florida. The mass shooting killed at least 50 people and injuring 53 others in what is the deadliest mass shooting in the country's history. (Photo by Joe Raedle/Getty Images)

ORLANDO, FL - JUNE 12: FBI agents investigate near the damaged rear wall of the Pulse Nightclub where Omar Mateen allegedly killed at least 50 people on June 12, 2016 in Orlando, Florida. The mass shooting killed at least 50 people and injuring 53 others in what is the deadliest mass shooting in the country's history. (Photo by Joe Raedle/Getty Images)

Friends and family members embrace outside the Orlando Police Headquarters during the investigation of a shooting at the Pulse night club, where as many as 20 people have been injured after a gunman opened fire, in Orlando, Florida, U.S June 12, 2016. REUTERS/Steve Nesius TPX IMAGES OF THE DAY

Demetrice Naulings sobs outside the Orlando Police Headquarters where police are interviewing witnesses in the investigation of a shooting at the Pulse nightclub, where people were killed by a gunman, in Orlando, Florida, U.S June 12, 2016. REUTERS/Steve Nesius

Concerned friends and family of victims of the Pulse nightclub shooting wait outside of the Orlando Police Department on Sunday, June 12, 2016. (Joe Burbank/Orlando Sentinel/TNS via Getty Images)

Ray Rivera, DJ at the Pulse nightclub, is consoled by a friend outside of the Orlando Police Department on Sunday, June 12, 2016. (Joe Burbank/Orlando Sentinel/TNS via Getty Images)

Police stand in front of one of the houses that officials indicated was connected to the Orlando shooter in Port St. Lucie, Florida, U.S. June 12, 2016. REUTERS/Joe Skipper

An aerial view shows the Pulse gay night club after a mass shooting in Orlando, Florida, U.S. June 12, 2016. REUTERS/Carlo Allegri

Police stand in front of one of the houses that officials indicated was connected to the Orlando shooter in Port St. Lucie, Florida, U.S. June 12, 2016. REUTERS/Joe Skipper

ORLANDO, FL - JUNE 12: FBI agents investigate near the damaged rear wall of the Pulse Nightclub where Omar Mateen allegedly killed at least 50 people on June 12, 2016 in Orlando, Florida. The mass shooting killed at least 50 people and injuring 53 others in what is the deadliest mass shooting in the country's history. (Photo by Joe Raedle/Getty Images)

ORLANDO, FL - JUNE 12: FBI agents investigate near the damaged rear wall of the Pulse Nightclub where Omar Mateen allegedly killed at least 50 people on June 12, 2016 in Orlando, Florida. The mass shooting killed at least 50 people and injuring 53 others in what is the deadliest mass shooting in the country's history. (Photo by Joe Raedle/Getty Images)

Officers arrive at the Orlando Police Headquarters during the investigation of a shooting at the Pulse nightclub, where people were killed by a gunman, in Orlando, Florida, U.S June 12, 2016. REUTERS/Steve Nesius

An aerial view shows the Pulse gay night club after a mass shooting in Orlando, Florida, U.S. June 12, 2016. REUTERS/Carlo Allegri

Orlando Police Chief John Mina and other city officials answer the media's questions about the Pulse nightclub shooting in Orlando, Florida June 12, 2016. REUTERS/Kevin Kolczynski

Police lock down Orange Avenue around Pulse nightclub, where people were killed by a gunman in a shooting rampage in Orlando, Florida June 12, 2016. REUTERS/Kevin Kolczynski